[PATCH v3 1/4] mm/page_isolation: make page isolation a standalone bit.

Zi Yan
2025-05-07T21:12:50Z

During page isolation, the original migratetype is overwritten, since
MIGRATE_* are enums and stored in pageblock bitmaps. Change
MIGRATE_ISOLATE to be stored a standalone bit, PB_migrate_isolate, like
PB_migrate_skip, so that migratetype is not lost during pageblock
isolation. pageblock bits needs to be word aligned, so expand
the number of pageblock bits from 4 to 8 and make PB_migrate_isolate bit 7.

Signed-off-by: Zi Yan <ziy@nvidia.com>
---
include/linux/mmzone.h | 17 ++++++++++----
include/linux/page-isolation.h | 2 +-
include/linux/pageblock-flags.h | 33 +++++++++++++++++++++++++-
mm/page_alloc.c | 41 ++++++++++++++++++++++++++++++++-
4 files changed, 86 insertions(+), 7 deletions(-)

diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index b19a98c20de8..9ec022a0b826 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -106,14 +106,23 @@ static inline bool migratetype_is_mergeable(int mt)

extern int page_group_by_mobility_disabled;

-#define MIGRATETYPE_MASK ((1UL << PB_migratetype_bits) - 1)
+#ifdef CONFIG_MEMORY_ISOLATION
+#define MIGRATETYPE_MASK ((BIT(PB_migratetype_bits) - 1) | PB_migrate_isolate_bit)
+#else
+#define MIGRATETYPE_MASK (BIT(PB_migratetype_bits) - 1)
+#endif

+#ifdef CONFIG_MEMORY_ISOLATION
+unsigned long get_pageblock_migratetype(const struct page *page);
+#else
#define get_pageblock_migratetype(page) \
get_pfnblock_flags_mask(page, page_to_pfn(page), MIGRATETYPE_MASK)

-#define folio_migratetype(folio) \
- get_pfnblock_flags_mask(&folio->page, folio_pfn(folio), \
- MIGRATETYPE_MASK)
+#endif
+
+#define folio_migratetype(folio) \
+ get_pageblock_migratetype(&folio->page)
+
struct free_area {
struct list_head free_list[MIGRATE_TYPES];
unsigned long nr_free;
diff --git a/include/linux/page-isolation.h b/include/linux/page-isolation.h
index 898bb788243b..51797dc39cbc 100644
--- a/include/linux/page-isolation.h
+++ b/include/linux/page-isolation.h
@@ -5,7 +5,7 @@
#ifdef CONFIG_MEMORY_ISOLATION
static inline bool is_migrate_isolate_page(struct page *page)
{
- return get_pageblock_migratetype(page) == MIGRATE_ISOLATE;
+ return get_pageblock_isolate(page);
}
static inline bool is_migrate_isolate(int migratetype)
{
diff --git a/include/linux/pageblock-flags.h b/include/linux/pageblock-flags.h
index 0c4963339f0b..9fadae5892b2 100644
--- a/include/linux/pageblock-flags.h
+++ b/include/linux/pageblock-flags.h
@@ -20,7 +20,10 @@ enum pageblock_bits {
PB_migrate_end = PB_migrate + PB_migratetype_bits - 1,
/* 3 bits required for migrate types */
PB_migrate_skip,/* If set the block is skipped by compaction */
-
+#ifdef CONFIG_MEMORY_ISOLATION
+ PB_migrate_isolate = 7, /* If set the block is isolated */
+ /* set it to 7 to make pageblock bit word aligned */
+#endif
/*
* Assume the bits will always align on a word. If this assumption
* changes then get/set pageblock needs updating.
@@ -28,6 +31,10 @@ enum pageblock_bits {
NR_PAGEBLOCK_BITS
};

+#ifdef CONFIG_MEMORY_ISOLATION
+#define PB_migrate_isolate_bit BIT(PB_migrate_isolate)
+#endif
+
#if defined(CONFIG_PAGE_BLOCK_ORDER)
#define PAGE_BLOCK_ORDER CONFIG_PAGE_BLOCK_ORDER
#else
@@ -105,4 +112,28 @@ static inline void set_pageblock_skip(struct page *page)
}
#endif /* CONFIG_COMPACTION */

+#ifdef CONFIG_MEMORY_ISOLATION
+#define get_pageblock_isolate(page) \
+ get_pfnblock_flags_mask(page, page_to_pfn(page), \
+ PB_migrate_isolate_bit)
+#define clear_pageblock_isolate(page) \
+ set_pfnblock_flags_mask(page, 0, page_to_pfn(page), \
+ PB_migrate_isolate_bit)
+#define set_pageblock_isolate(page) \
+ set_pfnblock_flags_mask(page, PB_migrate_isolate_bit, \
+ page_to_pfn(page), \
+ PB_migrate_isolate_bit)
+#else
+static inline bool get_pageblock_isolate(struct page *page)
+{
+ return false;
+}
+static inline void clear_pageblock_isolate(struct page *page)
+{
+}
+static inline void set_pageblock_isolate(struct page *page)
+{
+}
+#endif /* CONFIG_MEMORY_ISOLATION */
+
#endif /* PAGEBLOCK_FLAGS_H */
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index c77592b22256..acf68ef041d8 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -381,12 +381,40 @@ unsigned long get_pfnblock_flags_mask(const struct page *page,
return (word >> bitidx) & mask;
}

+#ifdef CONFIG_MEMORY_ISOLATION
+unsigned long get_pageblock_migratetype(const struct page *page)
+{
+ unsigned long flags;
+
+ flags = get_pfnblock_flags_mask(page, page_to_pfn(page),
+ MIGRATETYPE_MASK);
+ if (flags & PB_migrate_isolate_bit)
+ return MIGRATE_ISOLATE;
+
+ return flags;
+}
+
+static __always_inline int get_pfnblock_migratetype(const struct page *page,
+ unsigned long pfn)
+{
+ unsigned long flags;
+
+ flags = get_pfnblock_flags_mask(page, pfn,
+ MIGRATETYPE_MASK);
+ if (flags & PB_migrate_isolate_bit)
+ return MIGRATE_ISOLATE;
+
+ return flags;
+}
+#else
static __always_inline int get_pfnblock_migratetype(const struct page *page,
unsigned long pfn)
{
return get_pfnblock_flags_mask(page, pfn, MIGRATETYPE_MASK);
}

+#endif
+
/**
* set_pfnblock_flags_mask - Set the requested group of flags for a pageblock_nr_pages block of pages
* @page: The page within the block of interest
@@ -402,8 +430,14 @@ void set_pfnblock_flags_mask(struct page *page, unsigned long flags,
unsigned long bitidx, word_bitidx;
unsigned long word;

+#ifdef CONFIG_MEMORY_ISOLATION
+ BUILD_BUG_ON(NR_PAGEBLOCK_BITS != 8);
+ /* extra one for MIGRATE_ISOLATE */
+ BUILD_BUG_ON(MIGRATE_TYPES > (1 << PB_migratetype_bits) + 1);
+#else
BUILD_BUG_ON(NR_PAGEBLOCK_BITS != 4);
BUILD_BUG_ON(MIGRATE_TYPES > (1 << PB_migratetype_bits));
+#endif

bitmap = get_pageblock_bitmap(page, pfn);
bitidx = pfn_to_bitidx(page, pfn);
@@ -426,7 +460,12 @@ void set_pageblock_migratetype(struct page *page, int migratetype)
migratetype < MIGRATE_PCPTYPES))
migratetype = MIGRATE_UNMOVABLE;

- set_pfnblock_flags_mask(page, (unsigned long)migratetype,
+#ifdef CONFIG_MEMORY_ISOLATION
+ if (migratetype == MIGRATE_ISOLATE)
+ set_pageblock_isolate(page);
+ else
+#endif
+ set_pfnblock_flags_mask(page, (unsigned long)migratetype,
page_to_pfn(page), MIGRATETYPE_MASK);
}

--
2.47.2